284 EGYPTIAN AGRICULTURE. 



use in the sugar refineries, the bone black is renewed 

 by being again subjected to heat, but as the process is 

 repeated the percentage of carbon becomes reduced, and 

 the material is too poor in this ingredient to effectively act 

 as a filter. It is now "spent," and is technically known 

 as "spent char," which in Europe is used for the manu- 

 facture of superphosphates. In Egypt this material is 

 used in the raw state but a s however only one refinery 

 exists in the country, viz that at Hawamdieh, the total 

 production is very limited. 



Bat guano. Small quantities of this material are found 

 in rock crevices in Upper Egypt and are sometimes 

 employed as manure. Its inaccessibility, however, renders 

 it difficult and costly to procure. It varies greatly in 

 composition, the nitrogen ranging from \% to as much 

 as 9 % in exceptional cases. 



ARTIFICIAL MANURES. 



In the foregoing pages the substances discussed from 

 the point of view of their manurial properties have been 

 the ordinary residues of the farm from the feeding of 

 animals, and those substances of manurial value natural 

 to the country or produced in it frcm various industries. 

 With the intensive agriculture now in vogue the supplies 

 of these native manures are proving inadequate, and the 

 necessity of introducing into the country certain plant 

 foods in a highly concentrated form is every year becoming 

 more and more pronounced. 



